linux-kernel - Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu

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Message-ID: <4F47E47B.3000409@fb.com>
Date:	Fri, 24 Feb 2012 11:26:51 -0800
From:	Arun Sharma <asharma@...com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Balbir Singh <bsingharora@...il.com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu

On 2/23/12 6:47 PM, KAMEZAWA Hiroyuki wrote:
>>
>> In a distributed computing environment, a user submits a job to the
>> cluster job scheduler. The job might involve multiple related
>> executables and might involve multiple address spaces. But they're
>> performing one logical task, have a single resource limit enforced by a
>> cgroup.
>>
>> They don't have access to each other's VMAs, but if "accidentally" one
>> of them comes across an uninitialized page with data from another task,
>> it's not a violation of the security model.
>>
> How do you handle shared resouce, file-cache ?
>

 From a security perspective or a resource limit perspective?

Security: all processes in the cgroup run with the same uid and have the 
same access to the filesystem. Multiple address spaces in a cgroup can 
be thought of as an implementation detail.

Resource limit: We don't have strict enforcement right now. There is a 
desire to include everything (file cache, slab memory) in the job's 
memory resource limit.

  -Arun
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